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ARP Fridge Defend Install + First Impressions (in a 2019 315RLTS)

So you may have read my other thread on wanting to power my refrigerator on AC (through an inverter) while traveling. As a result of that thread and researching the forum I learned about ARP's Fridge Defend and absorption-style refrigerators (and what kills them). In the other thread I mentioned I also wanted to limit the logistics involved with the refrigerator. Another way of saying it is I want a configuration where I can "set it and forget it". The ARP device protects the refrigerator (from me) when I forget the frig is on and park on uneven ground.

As an interesting aside, I talked with the inventor today (Paul) and the ARP as it exists today came about due to stopping on a shoulder of a road (at a severe angle) while helping a fellow RV'er with a clogged fuel pump. By the time he was done helping the other guy he'd burned up his refrigerator, which he didn't realize until he arrived at his vacation destination. Today Paul was super with answering the phone (twice) to help me with install questions. On Christmas Eve no less!

2) Installing the ARP sensor is easier than it appears in the instructions, though it is a "blind" install. There will be scratched hands/arms, too, due to all the sharp edges where you're working. Removing the metal panel (the one with the schematic on it) makes it easier to work on the boiler.

In this picture the metal plate between the boiler and the ventilation panel is removed, but I haven't opened up the boiler itself.

3) A crimping tool is required (IMO) to make solid power connections for the fans (if you get that version). Extra lengths of wire are needed, too, if you decide to mount fans in the upper section or inside of the refrigerator. The length of wires on the fans are not long enough to reach the ARP controller. Extra insulation for around the heater tube and sensor is required as well.

4) Four sets of connectors for the fans are provided, but they are the typical ones you'll find at the hardware store. Not thrilled with how the connectors mate as metal is showing after they are connected (so 12V is exposed). I'm going to look for better connectors and replace what was sent. EDIT: I'm a dummy--all I needed to do was use heat shrink on the 12V+ connections. I have tons of it, too! Dang it...

5) If you decide to buy a Fridge Defend with the fan control (like I did) note that the large fan shown on the purchase option page (and the picture above) (https://www.arprv.com/purchase.php#number-four) does not fit in the upper ventilation section of my '19 315RLTS. The pictures below show the diagram from the installation manual at https://www.arprv.com/dometic-fan.php and what the upper section of my trailer looks like. There is no way (in my rig) the installation shown will work. The big fan won't fit anywhere in the upper space.

I installed both large fans in the lower ventilation panel. What I'm going to do is use the smaller fridge fans in the upper vent space as they fit perfectly between the vent slats. I talked with Paul about this and he's going to work with me on getting two more fans.

6) RTFMs. It's not immediately intuitive when power is applied what's going on. After reading the manual I discovered everything was working perfectly. (Whew.)

It's not a hard install but the blizzard of information on the website (and manuals) takes a while to absorb. (Get it?) I must have gone over the instructions (and watched the videos) 10 times before attempting to install the device.

If there's any questions fire away. I'll follow-up on this thread in the future when there's something new to report.

In the second drawing, are these fans to be attached to the removable opening cover?

Rob

Yes. I installed the two large ones in the lower vent cover (the air flow goes up). Only one was called for in the installation instructions but due to the second one not fitting in the upper vent cover I just doubled up on the bottom. Should have plenty of airflow now! They installed easily with zipties (red arrows). (The white ties are for the screens.)

Yes. I installed the two large ones in the lower vent cover (the air flow goes up). Only one was called for in the installation instructions but due to the second one not fitting in the upper vent cover I just doubled up on the bottom. Should have plenty of airflow now! They installed easily with zipties (red arrows). (The white ties are for the screens.)

Wouldn’t it make sense to turn those fans around so that they directly draw in outside air ?
(I admit that I haven’t read the ARP installation instructions )

Installed Defrost Fans in Refrigerator

BOTTOM LINE UP FRONT (BLUF)
If you have a Dometic RM1350SLMX, skip installing the defrost fans. It was not fun installing these things. As a boss used to say, "The juice isn't worth the squeeze." Get inexpensive battery powered fans and call it good!

THE DETAILS
It's hard to see in this before picture, but there's a removable drain pan that runs the width of the refrigerator. There's a plastic nipple that plugs into the back of the refrigerator that directs water down the exterior drain.

I wired the two fans in parallel and ran one wire to the lower vent area. As shown in the directions, I went through the drain hole. Unfortunately that plastic drain nipple is shaped like a funnel narrowing at the furthest end. The wires completely plugged it. I tried (carefully--or so I thought) to open up that nipple but the plastic immediately shattered in my hands. Grrrrr.... I spent the next hour fashioning a new drain nipple from an old motorcycle vacuum hose and used the Super Glue / Baking Soda trick to lock it into place. I was finally able to fish the wires through everything and get it all installed. The new drain setup doesn't look exactly stellar, but it's functional and doesn't leak.

Note that what you see below will not be the final installation. I'm going to get some white electrical tape to hide the wires inside the refrigerator. I had white masking tape (good stuff) but the DW said it would make the food taste bad. Nothing's open on New Year's Day, so I'll circle back to this later.

In the lower vent area (exterior of the trailer) of the refrigerator I drilled a 1/4" hole in the top of the drain line and fished the fan power wire through it. I then taped it up good with electrical tape. The fans are now connected to the ARP Controller and will turn on when the sensor attached to the return drain pipe exceeds a set temperature. (I think it's 90 degrees? I need to check that!)

Fire away if you have any questions. I'll update this thread after we actually use the refrigerator with the new ARP.

What wire size was used to push through the drain hole? Curious if given that the fans are very low current draw if you could use a much smaller wire gauge? I ponder this as I would like to add the ARP to my trailer on order with the Dometic fridge and will also have this problem...

What wire size was used to push through the drain hole? Curious if given that the fans are very low current draw if you could use a much smaller wire gauge? I ponder this as I would like to add the ARP to my trailer on order with the Dometic fridge and will also have this problem...

I don't know the exact size I used (found it in my scrap bin) but I'll call it "lamp cord". It was originally a 12V power cord for a cooler.

It was surprising how long I needed to make the wire that went through the drain hole and down to the controller. May have been close to 6'! The wires on the fans that come from ARP are not anywhere near the length needed. I took the time to solder the wires together and heat-shrink the connection where they join in the 'frig.

The wires on ARP's Defrost Fans are very, very small so you're right that they should draw little current.

What wire size was used to push through the drain hole? Curious if given that the fans are very low current draw if you could use a much smaller wire gauge? I ponder this as I would like to add the ARP to my trailer on order with the Dometic fridge and will also have this problem...

I thought about this more after my initial response. What I suggest is wait on the Defrost Fans until you have a chance to look at that drain pan setup yourself. It comes out of the refrigerator easily so you'll be able to test putting various wire combinations through that drain tube before committing to purchasing the Defrost Fans.

If I were to purchase the ARP today I'd still get the version with the fan controller, but I'd get one of the larger fans (for the lower vent area) and two of the small Defrost Fans for the upper vent area. Note that the recommendation is based on my experience installing the ARP system in a 2019 315RLTS with a 12 cu ft Dometic RM1350SLMX. Yours may be different.